Co0.85Se nanoparticles armored by N-doped carbon layer with electronic structure regulation functions: An efficient oxygen evolution electrocatalyst.

[Display omitted] • 1. The ball-flower hierarchical structure composites Co 0.85 Se-NC/C is synthesis. • 2. The introduction NC decreased the free energy and protected the nanoparticles. • 3. Co 0.85 Se-NC/C-750 exhibits a small Tafel slope of 47.2 mV dec-1 in 1.0 M KOH. • 4. DFT analysis showed superior intermediates adsorption property of Co 0.85 Se-NC. In this work, with the assistance of polymeric nonionic surfactant Pluronic F127, 2D nanosheets glycerol cobalt self-assembled into the ball-flower structure composites (CoG@F127). Then, CoG@F127 is coated by polydopamine (PDA) to form CoG@F127@PDA. After the calcination with Se powder, CoG@F127@PDA is transformed into the ball-flower hierarchical structure Co 0.85 Se-NC/C, in which Co 0.85 Se nanoparticles are coated with nitrogen doped carbon (NC). The Co 0.85 Se nanoparticles anchored on the NC can avoid the aggregation, maintain structure stability and expose more electrocatalytic active sites for oxygen evolution reaction (OER). Specially, Co 0.85 Se-NC/C-750 shows a small Tafel slope of 47.2 mV dec-1 in 1.0 M KOH that is even lower than IrO 2 and most of the reported Co-based catalysts. Besides, the theoretical calculations by density functional theory (DFT) suggest that NC could tailor the electronic structure of Co 0.85 Se, leading to optimized free energy change (Δ G) of the speed-controlled step and density of states (DOS). [ABSTRACT FROM AUTHOR]